ES2206936T3 - CELLULOSE MICROFIBER. - Google Patents

Abstract

THE INVENTION REFERS TO A PROCEDURE FOR THE MANUFACTURE OF CELLULOSE FIBERS, THE CELLULOSE DISSOLVING THROUGH A TERTIARY AQUAIN AMINE OXIDE IN A HILABLE SOLUTION, SPINNING THIS SOLUTION THROUGH THE USE OF A THREADING THREAD IN A FILAMENT FILAMENT PRECIPITATION EXTENDING THEM BY AN AIR PERFORMANCE, IN ORDER TO PRECIPITATE THE DISSOLVED CELLULOSE, CHARACTERIZED BECAUSE FOR THE THREADING A SOLUTION IS USED THAT PRESENTS LESS THAN 0.20% IN MASS, ESPECIALLY LESS THAN 0.05% IN MASS REFERRED TO MASS OF THE SOLUTION, CELLULOSE WITH A MOLECULAR WEIGHT OF, AT A MINIMUM, 5X10 5 AND BECAUSE THE AIR IN THE AIR RENDER PRESENTS A HUMIDITY OF LESS THAN 5 G OF WATER PER KG OF AIR.

Description

Cellulosic microfiber.

The present invention refers to a procedure for the manufacture of cellulosic fibers, at whose cellulose effect dissolves in an aqueous tertiary aminoxide forming a spinning solution, this solution is spun into filaments using a row, and the filaments are taken to a bath of precipitation with stretching through a slit of air, to precipitate the dissolved cellulose.

As an alternative to the viscose procedure, have described in recent years a series of procedures in the that cellulose dissolves, without formation of a derivative, in a organic solvent, a combination of an organic solvent with inorganic salt or in aqueous salt solutions. To the fibers of Cellulose that are manufactured based on such solutions were assigned by BISFA (International Bureau for Standardization of Synthetic Fibers) the generic name Lyocell. How Lyocell gets defines by BISFA a cellulose fiber that is obtained by a Spinning process of an organic solvent. How "organic solvent" means BISFA a mixture of a Organic chemical and water.

However, until today only one only procedure for the manufacture of a cellulose fiber from the genus Lyocell until industrial realization, and this is, in Actually, the aminoxide process. In this procedure you preferably used as solvent N-methylmorpholine-N-oxide (NMMO). For the purpose of this description, it will be used for concept "tertiary amino acids" the abbreviation "NMMO", for which NMMO also corresponds, in addition, to N-Methylmorpholine-N-oxide, used preferably today.

Tertiary amino acids have been known for a long time. time as alternative solvents of cellulose. Of the patent US-PS 2,179,181 is known as example that tertiary amino acids are able to dissolve without chemical cellulose derivatization of first quality and that of these solutions can be obtained, by precipitation, parts cellulosic molded as fibers. In US patents US-PS 3,447,939, 3,447,956 and 3,508,941 are described other procedures for the manufacture of cellulosic solutions, for which cyclic aminoxides are preferably used as solvents In all these procedures it dissolves physically Cellulose at high temperatures.

In the European patent EP-A-0 356 419 of the applicant is describes a procedure that is preferably performed in a thin film treatment apparatus in which a suspension of crushed cellulose extended in the form of a thin layer in a aqueous tertiary aminoxide, is transported on a surface heating for which the surface of this thin layer is subjected to a vacuum In the transport of the suspension by the surface water evaporates water and cellulose can dissolve so that from the film extruder a solution of hilarious cellulose.

Procedures for spinning solutions are known of cellulose, for example, of the European patent EP-A-0 671 492 and patent European EP-A-0 659 219 of the applicant. For this, the spinning solution is extruded by a row in the form of filaments that are driven by a slit of air to a precipitation bath in which cellulose precipitates. In the air slit the strands are stretched. This procedure is generally known as dry spinning method / via wet

Applicant's WO 95/02082 also describes a dry / wet spinning process. In this procedure is used cooling air at a temperature between 10ºC and 60ºC. The humidity of the conducted cooling air is per kilogram between 20 g H2O and 40 g H2O.

WO 94/28218 proposes in general the use of rows of 500 to 100,000 holes. The air temperature of refrigeration is between 0ºC and 50ºC. The person skilled in the art can deduce from this literature that the humidity is between 5.5 g H2O and 7.5 g H2O per kilo of air. This creates a relatively climate. Dry in the air gap.

WO 96/17118 also deals with the climate in the air gap, for which it is established that the weather should be as dry as possible, i.e. 0.1 g H2O up to 7 g H2O per kilogram of air, for a relative humidity of less than 85%. As a cooling air temperature, 6ºC is proposed up to 40 ° C

The same can be deduced from WO 96/18760, which proposes an air gap temperature between 10ºC and 37ºC and a relative humidity of 8.2% to 19.3%, which means 1 g H2O up to 7.5 g H2O per kilogram of air.

WO 96/21758 also deals with climate a adjust in the air gap for which a blow is proposed in two steps with different cooling air, and in which in the upper area of the air gap is blown with less humid air and colder

European patent EP-A-0 648 808 describes a procedure for molding a cellulose solution, for which cellulosic components of the solution contain a first component of a cellulose with an average degree of polymerization (DP) from 500 to 2000 and a second component of a cellulose with a DP of less than 90% of the DP of the first component in the 350 zone to 900. The proportion by weight of the first component with respect to the Second component should be from 95: 5 to 50:50.

It is known that in the aminoxide process they can only manufacture fibers with a lower grade than 1.7 dtex

The invention has the task of putting provision of a fiber manufacturing process cellulosics for which cellulose dissolves in an aminoxide aqueous tertiary in the form of a hilarious solution, this solution is  spin in filaments using a row, and the filaments are enter a precipitation bath through a slit of air and with stretching, to precipitate the dissolved cellulose, whose procedure allows to manufacture fibers of a title of a maximum of 1 dtex or lower These fibers are called microfibers ("Lexikon der Textilveredelung "(" Encyclopedia of Textile Finishing "), H.K. Rouette, volume 2, pages 1250 ss; nineteen ninety five; Laumann'sche Verlagsgesellschaft, ISBN 3-87466-228-4). The invention especially raises the task of putting arrangement of short fibers of the genus Lyocell of a maximum title or less than 1 dtex.

This objective is achieved according to the invention. why

(a) for spinning a solution is used, which it has less than 0.20% by mass, especially less than 0.05% in mass, referred to the mass of the solution, cellulose of a weight molecular of a minimum of 5x105, and

(b) the air in the air gap has a moisture content less than 5 g of water / kg of air.

Cellulose molecules of a molecular weight minimum of 5x105 are designated for the purposes of the present description and patent claims as "chain long. "

Surprisingly it has been shown that by combining the provisions indicated above (a) and (b) can be manufacture microfibers of a title less than 1 dtex. When using the solution specified in provision (a) impacts the content in moisture in the spinnability while this is better when lower the moisture content of the air in the slit of air.

This manifests itself in an especially intense way. when blowing the extruded filaments with dry air, that is, an air with a moisture content of 0%. Under these conditions you can manufacture fibers with a title of up to 0.30 dtex. The same cellulose when blowing with humid air (more than 30 g H2O / kg of air) It can transform into fibers of a 1.7 dtex title.

A preferred conditioning of the procedure according to the invention is characterized in that the filaments are they blow with air, immediately after they have left the row, because this air has a moisture content of less than 5 g of water / kg of air.

The method according to the invention is used tertiary aminoxide preferably N-methyl-morpholine-N-oxide.

The invention also refers to the use of a spinning solution of cellulose in an aqueous tertiary aminoxide, which has less than 0.20% by mass, especially less than 0.05% by mass, based on the mass of the solution, cellulose of a weight molecular weight of at least 5x105, for the manufacture of fibers cellulosics of a maximum of 1 dtex title.

How tertiary aminoxide has given the best results on N-methyl-morpholine-N-oxide.

The invention produces a cellulosic fiber of Lyocell genus, which presents a title in the area of 1.0 dtex to 0.3 dtex, especially in the area of 1.0 dtex and 0.5 dtex and, preferably, in the area of 1.0 dtex and 0.8 dtex. Analogously especially short fibers of a length from 1 cm to 10 cm.

In the process according to the invention you can use naturally all celluloses that have a part small enough of long chain cellulose molecules, so that these, after dissolution in aqueous aminoxide immediately before spinning they behave no more than 0.20% by mass. Celluloses with a larger part of long chain molecules only they can be used once the part in these has been reduced molecules which, for example, can be achieved by irradiation with electronic beam.

The invention is described below with more detail.

1. General method for determining the profile of the molecular weight of celluloses.

The molecular weight profile of a cellulose is can be obtained by gel permeation chromatography (GPC), for which a "Fraction of Weight" is recorded in a diagram Differential "in [%] as ordered based on molecular weight [g / mol; logarithmic representation).

The magnitude "Differential Weight Fraction" describes the percentage frequency of the molar mass fraction.

For analysis by GPC, cellulose is Dissolve in dimethylacetamide / LiCl and chromatography. It is detected by measuring the refractive index and the so-called measurement "MALLS" - (= Multiangular Dispersion of Laser Light) (Bomb HPLC: Fa. Kontron; sample collector: HP 1050, Fa. Hewlett Packard; medium: 9 g LiCl / L DMAC; RI detector: type F511, Fa. ERC; laser wavelength: 488 nm; dn / dc increase: 1.36 ml / g; analysis software; Astra 3d, version 4.2, Fa. Wyatt; material column: 4 column units, 300 mm x 7.5 mm, load material: PL Gel 20 µ - Mixed - A, Fa. Polymer-Laboratories; sample concentration: 1 g / l medium; injection volume: 40 µl, fluidity: 1 ml / min.

Measuring devices are calibrated using the custom measures of the technician.

The signal evaluation is performed according to Zimm, for which the Zimm formula must be adjusted, if necessary, in the analysis software

For Viscokraft LV cellulose (manufacturer: International Paper) weight profile is represented molecular, by way of example, in Figure 1a. The diagram of the fig. 1a shows that this cellulose is composed in a large part of molecules with a molecular weight of approx. 100,000 and that is cellulose  it has virtually no part with a molecular weight greater than 500,000 A 15% cellulose solution of exclusively this cellulose (see manufacturing below) in an aqueous aminoxide (= spinning mass) corresponds to that used according to the invention.

In comparison with this, fig. 1b shows the Alistaple LD 9.2 cellulose molecular weight profile (manufacturer: Western Pulp). In this cellulose the maximum of the frequency of molar mass at approximately 200,000, and the diagram also shows that this cellulose has a greater part (approx. 25%) of molecules with a molecular weight greater than 500,000. A spinning mass containing exclusively a cellulose of this class with 15% by mass, has approximately 4% (referred to the mass of the solution; regardless of the decrease during the manufacture of the solution) of cellulose molecules of a molecular weight greater than 500,000 and, thus, does not correspond to that used according to the invention.

2. Influence of irradiation on the weight profile molecular

To demonstrate the favorable influence of the irradiation in the molecular weight profile, it was irradiated Alistaple LD 9.2 cellulose in an acceleration apparatus 500 kV electrons with a radiation dose of 20 kGy (gas inert: mixture of CO2 and N2; temperature: 25ºC). By irradiation influence could be drastically reduced the part of long chain molecules and, actually, in an area that allowed the manufacture of cellulose solutions according to the invention.

3. Manufacture of cellulose solution

Crushed cellulose is suspended in aqueous NMMO at 50%, it takes a mixer (type: IKA-Laborkneter (laboratory mixer) HKD-T; maker: IKA-Labortechnik) and allowed to impregnate during a time. The water is then evaporated by heating the kneader by means of a heating medium heated to 130ºC and by reducing the pressure, until the cellulose has dissolved.

4. Solution spinning and speed determination maximum development

A spinning device is used as a spinning device merger index of the company Davenport, usual in the Plastics transformation. This device consists of a Heated steel cylinder, with temperature regulation, which is filled with the spinning dough. Through a plunger that it is loaded with a weight, the spinning mass is extruded through the row placed at the bottom of the steel cylinder, which it presents (the row) a hole with a diameter of 100 µm.

For the tests the spinning mass is extruded placed in the spinning apparatus (cellulose content: 15%) a through the hole and is conducted through an air gap with a length of 3 cm to an aqueous precipitation bath, diverted, carried by a roller provided behind the precipitation bath and, stretched out The amount of production through the row is 0.030 g / min The spinning temperature is from 80 ° C to 120 ° C.

For the simulation of spinning behavior the minimum spinning title is taken. For this, the maximum development speed (m / min). To this end, the development speed until the thread breaks. This speed is recorded and taken into account for the calculation of the title according to the formula indicated below. The higher this value is so much the spinning behavior is better and the finer the fiber obtained.

The title obtained at the speed of Maximum development is calculated with the following general formula:

\ text {Title} \ (dtex) = \ frac {1.21 \ x \ K \ x \ A \ x \ 100} {G \ x \ L}

where K is the cellulose concentration in% in mass, At the amount of production in g / minute, G the speed of development in m / minute and L the number of holes in the row. For the examples that appear below the concentration of Cellulose is 15%, A = 0.030 g / minute and L = one.

5. Adjusting the humidity of the air in the slit of air

For air humidity adjustment in the air slit cools supersaturated air with water vapor by means of a device with thermostat, it adjusts to the humidity corresponding and blow in the air slit, at right angles and in the entire length of the filament.

Comparative examples

According to the work systems described above, made a spinning mass with cellulose (not irradiated) Alistaple LD 9.2 (manufacturer: Western Pulp), whose weight profile molecular is represented in fig. 1b, spun into the slit of air at various temperatures and then the speed of  maximum development or, the minimum hilarious title. The results they are indicated in table 1.

In table 1 and in the following tables "Temp." means the temperature in ºC, "humidity" the air humidity in the air gap in g of water / kg of air and "Maximum development speed" development speed Maximum in m / minute. The title was calculated according to the previous formula and the dtex unit is applied.

TABLE 1

one

The results represented in table 1 show the relationship that the maximum development speed increases and the minimum titer decreases with increasing humidity in the air slit This means that by increasing the humidity you can spin a thread of smaller title. However, the fibers of a title less than 1 dtex can only spin with difficulty and manufacture with extraordinarily high humidity.

Examples according to the invention

According to the work systems described above, made a spinning mass with cellulose (not irradiated) Viscokraft LV (manufacturer: International Paper Corp.) whose profile of molecular weight is represented in fig. 1st and spun on the air gap at various temperatures and humidity and then determined the maximum development speed or the minimum title hilarious The results are indicated in table 2.

TABLE 2

two

The results represented in table 2 show the relationship according to the invention that when using the dough of spinning according to the invention the speed of maximum development if the humidity in the air gap is reduced. From This way it is possible to manufacture finer fibers. It is also achieved manufacture fibers with a title of up to 0.3 dtex.

Similar good results could also obtain with irradiated cellulose, above, Alistaple LD 9.2.

6. Spinning behavior of cellulose solutions with variable parts of long chain molecules

According to the work system described above, made a 15% mass by mass of a 30% mixture of Alistaple LD 9.2 and 70% of Viscokraft LV. The cellulosic mixture had a distribution of the distribution immediately before spinning molecular weight as in fig. 1 C. The spinning mass was spun at a temperature of 120 ° C at various humidities in the air gap. The result of these tests is indicated in the following table 3:

TABLE 3

3

Obviously it can be seen in Table 3 that difference of a spinning mass with 15% cellulose Viscokraft there is no worsening of the minimum title that can be get by increasing the temperature in the air gap but that even a slight improvement can be obtained. However, in comparison with a spinning mass with 15% cellulose Alistaple can be achieved, as seen, smaller titles.

Fig. 2 shows spinning behavior of cellulose solutions with variable parts of molecules of long chain, for which the title is represented in the ordinate minimum (dtex) and in the abscissa the concentration of the solution of corresponding cellulose in cellulose molecules of a weight molecular of at least 500,000. The concentrations are determined immediately before spinning.

The part of long chain molecules was adjusted mixing the corresponding amounts of Alistaple LD 9.2 and Viscokraft LV. The cellulose concentration of the mixture was in All cases 15% by mass.

Spinning behavior was determined to each cellulose solution for moisture in the air gap of 30 g H 2 O (curve "a") as well as for 0 g H 2 O (dry) (straight "b").

From figure 2 it can be deduced:

-

that there is a relationship between hilability and the concentration of molecules of long chain;

-

that in the case of dry air in the air gap (straight "b") hilability, approximately linear, it is always better if the concentration of long chain molecules;

-

that in the case of moist air in the air slit (curve "a") spinning at the beginning it is always better when the concentration of long chain molecules, however, decreases again from of a concentration of approx. 0.25% by mass, being especially significant this worsening from 0.05% in mass.

Figure 2 shows that for the manufacture of Microfibers should take into account two critical quantities:

-

the concentration in cellulose molecules of a molecular weight of at least 5x105, Y

-

the content in air humidity in the air gap.

Claims (4)

1. Procedure for the manufacture of fibers cellulosics for which cellulose dissolves in an aminoxide aqueous tertiary in the form of a spinning solution, this solution it is spun in filaments using a row, and the filaments are enter a precipitation bath through a slit of air and with stretching, to precipitate the dissolved cellulose, characterized because

-

to spin it is used a solution, which has less than 0.20% by mass, especially less than 0.05% by mass, based on the mass of the solution, cellulose  of a molecular weight of at least 5x105, and

-

the air in the air gap has a moisture content of less than 5 g of water / kg of air

2. Method according to claim 1, characterized in that the filaments are blown with air, immediately after they have left the row, and because this air has a moisture content of less than 5 g of water / kg of air. 3. Method according to one of claims 1 or 2, characterized in that N-methyl-morpholine-N-oxide is used as the tertiary aminoxide. 4. Use of a spinning cellulose solution in an aqueous tertiary aminoxide, which has less than 0.20% in mass, especially less than 0.05% by mass, based on the mass of the solution, cellulose of a molecular weight of at least 5x105, for the manufacture of cellulosic fibers of a maximum 1 title dtex